Do Allergies Cause Asthma?

My daughter has asthma and I'm worried that her younger brother might develop it, too. He has seasonal allergies and I've heard that allergies can cause asthma. Is this true?- Elisha

No, allergies do not cause a person to develop asthma. But these two conditions are related, so it's natural to assume that one might lead to the other. Kids with allergies (especially allergies that affect the nose and eyes) are more likely to have asthma than those who don't. The same goes for kids who have a family history of allergies or asthma — they're more likely to develop one or both conditions.

So, based on your son's family history and the fact that he has allergies, he does have an increased risk of developing asthma. But that doesn't mean that he definitely will. Many people with allergies never develop asthma.

Where there might be some confusion about allergies and asthma is that sometimes a person who already has asthma, like your daughter, can have symptoms worsen if she's exposed to specific allergens (things that cause an allergic reaction). In fact, up to three quarters of kids who have asthma also have an allergy to something.

With any kind of allergy, the immune system overreacts to normally harmless substances, such as pollen or dust mites. As part of this overreaction, the body produces an antibody of the immunoglobulin E (IgE) type, which specifically recognizes and attaches to the allergen when the body is exposed to it. When that happens, it sets a process in motion that results in the release of certain substances in the body. One of them is histamine, which causes allergic symptoms that can affect the eyes, nose, throat, skin, gastrointestinal tract, and lungs. When the airways in the lungs are affected, the symptoms of asthma can occur.

Future exposure to the same allergens can cause the reaction to happen again. So, in your daughter's case, it's wise to explore whether allergies may triggering some of her asthma symptoms. Talk to her doctor, who can identify possible triggers. Triggers can be things other than allergens, such as cold air, respiratory infections, or tobacco smoke.

If allergens are found to be an important trigger for her asthma symptoms, do what you can to help your daughter avoid exposure to the allergens involved. (If this doesn't help control the asthma symptoms, the doctor also might prescribe medications or allergy shots.)

And as for your son, do your best to help him avoid any allergy triggers he may have. If you think he's beginning to show the signs of asthma, take him to the doctor for a full evaluation.